An examining insertion tube is a promising examination apparatus, which is used for observing the inside of a narrow space (inside of a pipe or a gap, etc.) where human body cannot enter or for observing the state in the vessel or the organs inside the human body without cutting to open the human body. This examining insertion tube generally has an observation means at the head end and an operating mechanism at the bottom end, and is designed for the end portion to be bent in any direction by the operating mechanism.
As a conventional technology, a freely flexible tube (Japanese Patent Application Nos. Hei 5[1993]-253171 and 253172) which provides an observation device around the head end portion and a bending mechanism which bends the observation device in a prescribed direction can be cited.
The bending mechanism is provided with multiple joint members and a bending application means which energizes the bending operation in each joint member and this bending application means is comprised of a wire-like shape memory alloy stretched between the joint members and a heater which heats this shape memory alloy. Namely, according to this constitution, the heated shape memory alloy contracts to its original length and application in the bending operation between the joint members is achieved by utilizing the tensile force [generated] during this contraction.